Dwain Chambers "must learn the hard way" if he is to make a successful comeback from his two-year ban imposed for taking steroids, according to Olympic great Sebastian Coe.
Former 100 metres European champion Chambers is expected to return to the track at the Norwich Union Grand Prix in Birmingham on February 18.
Chambers was banned for two years after being found guilty of taking the designer steroid THG. The IAAF also want him to return some of the prize money he won in the year before his positive test in August 2003.
Coe, who regards Chambers as a personal friend, said the 27-year-old had been led astray and would find it tough to get back to his old level.
"I hope Dwain has learned to know where his friends in the sport are, and that there are no quick solutions," said Coe, double Olympic champion and chairman on London 2012.
"I sincerely hope he can get back to his old level. It's difficult to be out of competitive sport for that length of time and to bounce back but Dwain must learn the hard way about who his friends in the sport are.
"The thing I found saddest about the whole situation, and I'm biased because he's a close friend of mine, is that Dwain was making pretty good progress with [former coach] Micky McFarlane and when Tim Montgomery broke the world record in Paris, Dwain was a pretty close second.
"That relationship with Micky was a model of excellence and I'm just sorry that Dwain got diverted by people who frankly shouldn't be involved in the sport."
Coe believes Chambers had huge potential and will have to put his troubles behind him.
He added: "I'm not piling agonies onto the problems that Dwain confronted.
"I saw big potential in him and he got sidetracked by people who did not have his interests at heart."
Coe was speaking at the ticket launch of the 2007 European athletics indoor championships to be held in Birmingham in March next year.
